Weevil Damage Research Articles

Sweetpotato production practices, constraints, and variety evaluation under different storage types

AbstractSweetpotato plays an important role in ensuring food security and household income sources for local communities in Ethiopia. It is dominantly grown in southern parts of Ethiopia. However, its production and productivity over the last few years has declined due to the limited access of quality planting materials at the onset of the rainy season, disease, and severe pest infestation. Therefore, it was imperative to carry out this study to identify the main constraints related to the recent decline of the crop in Misrak Badawacho District. The survey result revealed that many varieties of sweetpotato were grown in the district; mainly, Awassa‐83, Ogan‐Sagan, and Wolaita‐local were the most preferred variety by producers. The main sweetpotato production and storage constraints in the study district are as follows: rodents, disease and insect pests, heat and drought, shortage of quality planting materials, and absence of best methods for long‐term storage. Awassa‐83, Ogan‐Sagan and Wolaita‐local were evaluated under different storage types (straw, soil, ash, sawdust, and sand storage). The combination of Awassa‐83 variety and sand storage was performed better in percentage of decay, weight loss, and weevil damage, whereas length and number of vine per storage roots were performed better in the separate treatment. Thus, Awassa‐83 variety and sand storage can be recommended for maintaining the storage roots during dry periods and access of quality vines at the onset of the rainy season. More importantly, sand storage provides an opportunity to maintain the quality of sweetpotato storage roots for a long period of time and producers can easily and timely access quality vines at the onset of rainy season.

Screening of sweetpotato germplasm collections for sweetpotato weevil (Cylas spp.) resistance in Tanzania

Weevil damage caused by sweetpotato weevil (Cylas spp.) is a major constraint to sweetpotato production in Tanzania due to a lack of improved varieties with durable resistance. The objective of this study was to screen sweetpotato germplasm collections for weevil resistance and to select the best parents to be used in resistance breeding. Field studies involving 96 sweetpotato genotypes were conducted at two weevil hotspot sites in Western Tanzania using a 12 x 8 lattice design with three replications at each site. Data collected included yield and yield related traits, weevil reaction and weevil damage score. The tested genotypes differed significantly (P < 0.01) for sweetpotato storage root number, root weight, root infestation and root damage score. Weevil infestation on storage roots significantly (P ≤0.05) correlated with total root number (r = 0.38) and weevil damage score (r = 0.79). Marketable root weight and total root weight were significantly correlated with infested root weight each with r = 0.45. The study identified nine sweetpotato genotypes expressing resistance and 10 genotypes with moderate resistance to weevil. Five genotypes including Magunhwa, Chuchu ya Nesi, Rugomoka, Tumauma and New Kawogo were selected with weevil resistance and desirable yield and yield-related traits. These genotypes can be used in future weevil resistance breeding programs of sweetpotato in Western Tanzania or related agro-ecologies.

Temporal effects of biocontrol processes on nutrient dynamics in a shallow lake: Case study of Lake Xini, Okavango Delta in Botswana

Little is known about the effects of weeds on nutrient concentration changes in aquatic environments. We examined alterations to nutrient dynamics from the biocontrol process of Salvinia molesta by the weevil Cyrtobagous salviniae in the Lake Xini of Okavango, Botswana. The abundance of weevils steadily increased from March to December 2009 in the range of 15 to 62 ind. kg−1 fresh biomass with 93% bud damage at the time of mat sinking. Dissolved oxygen was 1.2 mg l−1 with >90% salvinia coverage in March 2009 and increased to 4.56 mg l−1 after 12 months of biocontrol, when salvinia cover was reduced to <10% cover. The study was conducted by placing plastic containers in the lake containing 1 kg weevil infested salvinia and water from the lake. The declines in weevil-damaged ‘floating salvinia’ were inversely proportional to the increases in ‘salvinia detritus’ in the study containers. Leaching of nutrients (N and P) and major ions (Ca, Mg, Na and K) in floating salvinia and salvinia detritus, as a result of weevil damage, showed P and K consistently leached at higher rates. Nutrients in the lake were high during biocontrol process, compared with after control. Biocontrol resulted in an increase in dissolved oxygen and re-emergence of native vegetation.

CONTROL DE GORGOJO (Sitophilus zeamais MOTSCHULSKY) CON POLVOS DE EPAZOTE (Dysphania ambrosioides (L.) MOSYAKIN &amp; CLEMANTS) EN DIFERENTES GENOTIPOS DE MAÍZ

Durante el manejo postcosecha del maíz (Zea mays L.) se presentan pérdidas importantes por el ataque de plagas de almacén, particularmente por gorgojo (Sitophilus zeamais Motschulsky). El objetivo del presente estudio fue evaluar la efectividad del epazote (Dysphania ambrosioides) para controlar los daños por gorgojo en maíz. Semillas de 11 genotipos de maíz, nueve experimentales y dos híbridos comerciales, todos con humedad de 13 % y sin daño físico que indicara la presencia de insectos, fueron sometidos a tratamientos con polvo de epazote en cuatro concentraciones (0, 5, 7 y 10 g de epazote kg-1 de semilla) para controlar gorgojo. Se utilizó un diseño completamente al azar con arreglo factorial y tres repeticiones. La unidad experimental consistió en una caja de plástico acondicionada donde se colocaron 100 semillas, previamente pesadas, junto con 50 gorgojos jóvenes y la dosis correspondiente de polvo de epazote. Las variables registradas fueron pérdida de peso, granos dañados y sobrevivencia de insectos, todos expresados en porcentaje. Hubo diferencias entre genotipos de maíz solamente para pérdida de peso (P ≤ 0.05); todos los genotipos de maíz registraron pérdidas; sin embargo, el híbrido CLTHW14001 fue el menos afectado con 3.5 % de pérdida de peso. Las dosis de 7 y 10 g de epazote kg-1 de semilla fueron sobresalientes en las variables pérdida de peso, granos dañados y sobrevivencia de insectos, con 3.4, 12.2 y 3.5 % en promedio, respectivamente. El híbrido CLTHW14001 mostró el menor daño con la dosis de 7 g de epazote kg-1 de semilla con 0.94 % de pérdida de peso. El uso de polvo de epazote para el control de gorgojo es efectivo en concentraciones desde 7 g kg-1 de semilla. El genotipo de maíz influye en la efectividad del tratamiento.

Evaluation of early-generation tropical maize testcrosses for grain-yield potential and weevil (Sitophilus zeamais Motschulsky) resistance

Smallholder maize farmers in Africa experience pre- and post-harvest production stresses either individually or in combination at different stages of the crop cycle. The maize weevil is among the major post-harvest storage pests. A strategy to address this problem is to develop and promote high yielding maize germplasm with resistance to multiple stresses. A study was conducted to: 1) assess yield and agronomic performance of testcross hybrids developed from early generation lines; and 2) assess the response of the testcross hybrids to infestation with Sitophilus zeamais. Fifty-eight drought-tolerant testcross hybrids were evaluated for agronomic performance and weevil resistance at four environments in Uganda in 2016. Hybrid G39 (L2/T2) had the best grain yield performance; it significantly out-performed the best check by 11.4% in all environments. Hybrid grain from field trials was subjected to Sitophilus zeamais infestation in a choice and no choice test under laboratory conditions. Hybrids G56 (L49/T2) and G58 (L51/T2) had the least weevil damage and were rated as resistant to Sitophilus zeamais. The numbers of damaged kernels, number of exit holes and ear aspect were positively correlated with the grain weight loss. The results suggest possibilities for simultaneous selection for high grain yield and storage insect pest resistance among drought-tolerant genotypes. Use of high-yielding and resistant maize hybrids to storage insect pest should be promoted for increased maize production and managing post-harvest losses due to the maize weevil in smallholder farming communities in Africa.

Assessment of Low-cost Postharvest Techniques to Reduce Storage Losses in Sweet Potato

Sweet potato is now classified among the high-priority crops targeted at reducing food insecurity and malnutrition in many countries. Despite this growing interest, high postharvest losses caused by poor handling, physiological weight loss, sprouting, weevil (Cylas spp.) damage and microbial decay remain a challenge. Decay losses due to tip rot and other pathogenic fungi are a challenge in Ghana. Incidence of tip rot, which is characterized by a dry decay at either or both ends of roots, is severe due to late harvesting of roots which are intended for storage. This study evaluated a series of postharvest techniques which can be integrated to extend shelf-life in small scale storage. These include harvest maturity, root tip coppicing, hot water treatment, honey waxing and sanitizing in postharvest chemicals. Tip coppicing significantly (P&amp;lt;0.001) reduced the incidence of tip rot across the varieties when stored for 8 weeks, but dipping roots in different oils did not significantly (P&amp;lt;0.05) reduce tip rot incidence. Decay losses in the control and hot water treated roots were similar during the first 4 weeks after storage, but later losses were significantly severe in hot water treated roots. The range of fungi genera identified in this study are generally fungal endophytes; often symptomless in roots but become pathogenic when conditions are favourable. Due to the root thin skin, mechanical injuries during harvesting and handling become infection pathways for such pathogens. Therefore, integration of best practices at each step of harvesting and postharvest handling operations can significantly minimize decay losses.

A method for reconstructing the internal morphological structure of wheat kernels upon Sitophilus zeamais infestation

Weevils (Sitophilus zeamais) are the most harmful stored-grain pest, and they appear as damage inside wheat kernels. The morphological changes to the inner kernel structure that occur after weevil infestation have not been thoroughly studied. Rapid and non-destructive methods for studying weevil damage would be readily accepted by the grain storage and quality control industry. Traditional research methods for investigating the morphological structures of kernels are mostly destructive and two-dimensional (2D) and cannot provide information on the three-dimensional (3D) spatial structure inside a kernel in a non-destructive and complete manner. X-ray Micro-Computed Tomography (X-ray μCT), a non-destructive 3D imaging and analysis technique used for studying the internal structure of a variety of materials, has great potential for application in the field of cereal science. To this end, this study involved a non-destructive imaging method based on X-ray μCT for measuring and characterizing the morphological structure of wheat kernels infested with S. zeamais. Through this method, X-ray μCT was used to acquire high-resolution 2D tomographic images (referred to here as 2D slices), which were subjected to noise reduction, filtering, segmentation, and reconstruction for the 3D visualization of the morphological structure inside S. zeamais-infested wheat kernels. A quantitative analysis of key parameters reflecting the changes in the morphological structure was also performed. The following results were obtained: (1) Based on differences in grayscale values in the 2D slices, the complex anatomical features inside the kernels were distinguished, and patterns of change in the components inside the kernels were determined successfully. (2) Using a 3D visualized characterization of the morphological structure, detailed spatial descriptions of the structural damage inside S. zeamais-infested kernels were achieved when S. zeamais was at different life stages. (3) A quantitative analysis was performed on the changes in key parameters in specific tissues inside S. zeamais-infested wheat kernels at different stages. As S. zeamais development progressed, certain insect parameters and the holes in the kernels caused by the S. zeamais feeding processes inside the kernel increased. The changes were particularly notable at 22 d of S. zeamais development, when the hole accounted for approximately 21% of the entire wheat kernel.

Seasonal timing and recurrence of methyl jasmonate treatment influence pine weevil damage to Norway spruce seedlings

Defense can be induced in conifer seedlings to reduce pine weevil (Hylobius abietis) damage, by treatment with the plant hormone methyl jasmonate (MJ). Few studies have addressed important practical issues regarding the use of MJ such as treatment incidence and timing, seedling age and its compatibility with plant nursery practices. We examined if levels of pine weevil damage depend on seasonal timing and recurrence of MJ treatment, and if the observed effects depend on plant age. Norway spruce (Picea abies) seedlings from two age cohorts (1 year and 1.5 years old) received four MJ treatments: MJ application before winter storage in the previous year, after winter storage but before spring/summer planting, repeated MJ application (both before winter storage, and before planting) or no MJ application at all. Pine weevil damage was evaluated in a lab and field experiment. We found that the timing and recurrence of MJ treatment affected the amount of damage inflicted by pine weevils in different ways, but these effects were consistent among age cohorts. MJ application before winter storage provided the most effective protection, and this reduction in damage was comparable to that provided by a currently used physical protection method against pine weevil feeding. Our results indicated that MJ can be applied in line with nursery practices (before winter storage) and provides adequate protection for two growing seasons.

Non‐pesticide alternatives for reducing feeding damage caused by the large pine weevil (Hylobius abietis L.)

AbstractThe large pine weevil (Hylobius abietis L.) is an important pest of young forest stands in Europe. Larvae develop under the bark of freshly cut pine and spruce stumps, but maturing weevils feed on the bark of coniferous seedlings. Such seedlings frequently die because of bark consumption near the root collar. We tested the effect of three treatments (the insecticide alpha cypermethrin, a wax coating and a glue coating) on the feeding damage caused by H. abietis on Douglas fir (Pseudotsuga menziesii) and Norway spruce (Picea abies) seedlings under semi‐natural conditions. In two experiments (one in 2016 and another in 2017) seedlings in cages were subjected to pine weevil feeding for 16 weeks under shaded outdoor conditions. The experiment in 2016 compared insecticide and wax treatments and an untreated control on Douglas fir and Norway spruce, and the experiment in 2017 compared insecticide, wax and glue treatments and an untreated control on Norway spruce. In both experiments, all treatments significantly reduced H. abietis feeding damage at week 8 at the end of both experiments (week 16); the effect of treatments was significant only on spruce seedlings. The damages on Douglas fir seedlings was less on treated seedlings than on untreated control seedlings but differences were not significant. Coating stems with glue and especially with wax was generally effective at reducing weevil damage and in most cases provided control that was not significantly different from that provided by insecticide treatment. Our results suggest that a wax coating has the potential to replace the protection of seedlings provided by insecticides.

Does stump removal reduce pine weevil and other damage in Norway spruce regenerations? – Results of a 12-year monitoring period

Although impacts of intensive forest harvesting practices such as removing logging residue and stumps for bioenergy on forest ecosystem has been extensively studied, no information is available about the long-term effects of stump harvesting on the health status of young Norway spruce stands. In the present study, we surveyed damage caused by the large pine weevil (Hylobius abietis L.) and other causal agents as well as the height growth of the Norway spruce seedlings for 12 years in stump-harvested and non-harvested experimental plots. The overall effect of stump harvesting combined with mounding on the health and survival of spruces was positive: 70% of spruce seedlings in stump-harvested plots were spared any damage, while 58% of seedlings remained undamaged in undisturbed control plots. The positive effect of stump removal and mounding on tree health was mainly due to reduced pine weevil damage. In all, 14.8 and 24.6% of spruce seedlings were gnawed by pine weevil in stump-harvested and control plots, respectively. In stump-harvested plots, pine weevil damage was slighter and lasted for a shorter time than in control plots. In addition, damage caused by Hylastes spp., black root beetles, was significantly less on stump-harvested plots. By contrast, vole damage was most frequent in stump-harvested plots during the population peak when the vole density was exceptionally high. Irrespective of whether stumps were harvested or not, stump roots provided a source of Heterobasidion inoculum in the next spruce regeneration. During this early stage of stand development only a few spruce seedlings were killed by Heterobasidion root rot and there were neither temporal nor quantitative treatment-related differences between the treatments. From the third year onwards the height growth of undamaged seedlings was more rapid in stump-harvested than non-harvested plots. Our results suggest that the overall risk of damage in young Norway spruce stands can be reduced by stump harvesting. Thus, stump harvesting and mounding seem to decrease the need for supplementary planting, which reduces regeneration costs that represent a considerable financial investment for a forest owner.

Exophthalmus cupreipes Champion (Coleoptera: Curculionidae) in Citrus Crops in Mexico

Exophthalmus cupreipes Champion (Coleoptera: Curculionidae) adult weevils were detected feeding on young leaves and shoots of Persian limes (Citrus latifolia [Tanaka ex Yu. Tanaka] Tanaka; Rutaceae) in commercial plantations in the states of Veracruz and Tabasco, Mexico. Weevil damage to foliage is apparently not significant enough to cause production losses. However, there are reports of related species included in the Exophthalmus genus complex that are considered primary pests of agriculturally important citruses. This study complements the original description by Champion (1911) for adults of both sexes, and provides images of external and internal structures useful for its identification. Moreover, field observations of damage on citrus are presented, and the potential importance as a pest is discussed.

Inter-disciplinary analysis for synthesising weevil damage and stakeholder perception related to stump harvesting

Inter-disciplinary analysis for synthesising weevil damage and stakeholder perception related to stump harvesting

English

Creating a nursery for sweet potato cultivation in tropical and subtropical areas including Okinawa is not necessary because planting is possible throughout the year. In general, sweet potato blooms under natural conditions in tropical and subtropical areas. Sweet potatoes are grown from non-flowering slips, which farmers generally select from a field of a previous cropping. Although the selection and collection of non-flowering slips are very time-consuming, the effect on yield when flowering slips are used is unknown. This study sought to investigate the effect of flowering on sweet potato yield. The results revealed no significant difference in yield between flowering and non-flowering slips. This can significantly reduce the preparation time of slips, shorten the working time of the farmers and is useful for sweet potato cultivation in tropical and subtropical areas. Key words: Convolvulaceae, sweet potato cultivation, weevil damage. &nbsp

Screening barrier plants to reduce crop attack by sweet potato weevil (Cylas formicarius).

Sweet potato weevil, Cylas formicarius (Fabricius) attacks stems and storage roots of sweet potato, Ipomoea batatas, and is a major pest of this globally significant crop. To minimize the immigration of weevils into sweet potato fields from nearby donor habitat, we assessed scope for a barrier plant approach. Here, we report a novel, two-stage, multiple choice olfactometer method to screen candidate barrier plant species and a field study of the effects of shortlisted barrier plants of weevil movement and plant damage. Initial work established that a combination of sweet potato foliage and storage root was significantly more attractive to adult C. formicarius than either tissue alone in the distal chamber of choice arms. Among 15 candidate barrier plant species in intermediate chambers in arms, spring onion, oregano, chilli, basil, sweetcorn, fennel, lime mint and lemongrass significantly reduced passage of C. formicarius. Of these, sweetcorn and lime mint significantly reduced the numbers of oviposition holes in sweet potato storage roots. A field study showed that basil and chives were effective barrier plants for reducing weevil damage to sweet potato storage roots. Our method has utility for screening additional candidate plants, and suggests that weevil dispersal and subsequent oviposition are affected by passage through some plants, suggesting scope for barrier plants to contribute to the management of this major pest. © 2019 Society of Chemical Industry.

Genome-Wide Association Studies (GWAS) for Yield and Weevil Resistance in Sweet potato (Ipomoea batatas (L.) Lam).

We apply the GWAS to sweet potato genome, and identified the SNPs associated with yield and weevil resistance. The sweet potato (Ipomoea batatas (L.) Lam) is a highly heterozygous, outcrossing, polyploid species, which presents challenges for genetic analysis. Therefore, we considered that genome-wide association studies (GWAS) may be applied to the study of the sweet potato genome. The yield of two sweet potato varieties [Purple Sweet Lord (PSL) and 90IDN-47] was assessed at two locations (Kumamoto and Okinawa prefectures) in Japan in 2013 and the yield scores were used for GWAS. The results showed that there were several single nucleotide polymorphisms (SNP) above the significance thresholds in PSL; two peaks were detected in Kumamoto and Okinawa on the Ib03-3 and Ib01-4 linkage groups of PSL, respectively. As for 90IDN-47, one relatively high peak was detected in Kumamoto on the Ib13-8 linkage group. Interestingly, although high peaks above significance thresholds were detected in Kumamoto and Okinawa in PSL, the peaks were located in different linkage groups. This result suggests that the genetic regions controlling yield may change in response to environmental conditions. Additionally, we investigated the degree of weevil damage to the plants, which is the greatest problem in sweet potato cultivation in Okinawa. In this experiment, no SNPs were identified above the significance thresholds. However, one relatively high peak was found in the 90IDN-47 genotype, which showed resistance to weevils. On the other hand, one relatively high peak was also detected in the PSL genotype, which showed susceptibility to weevils. These results suggest that two regions could affect weevil resistance and may contain the gene(s) controlling weevil resistance.

Phenotyping tree resistance to a bark‐chewing insect, the pine weevil Hylobius abietis

AbstractBreeding for resistance to forest pests and pathogens is emerging as a promising tool for minimising the impact of the increasing biotic threats that our forests are experiencing as a consequence of global change. Efficient phenotyping protocols of resistance are urgently needed. Here we present the results of two experiments aimed to determine whether the variation in resistance to the pine weevil Hylobius abietis, a harmful pest of European conifers, can be inferred by nondestructive bioassays using excised plant material collected in forest genetic trials. Weevil damage and amount of nonvolatile resin induced by weevil feeding were assessed in young trees and in branches of adult trees using several phenotyping procedures (bioassays using either living trees, excised plant material and cut stem twigs) on four pine species (Pinus pinaster, P. radiata, P. sylvestris and P. pinea). Half of the plants were previously induced with methyl jasmonate (MJ), a treatment that is known to affect resistance to the pine weevil. In Experiment 1, living and excised plants showed parallel results: MJ treatment significantly reduced weevil damage, and saplings responded to weevil damage locally increasing the nonvolatile resin (NVR) in the stems proportionally to the damage suffered. This response was, however, slightly lower in excised than in living saplings. On the contrary, patterns of weevil feeding on stem twigs completely departed from those observed in living and excised seedlings. Moreover, cut stem twigs were unable to respond to weevil feeding increasing NVR according to the weevil damage. In Experiment 2, assessment of weevil damage on excised branches explained around 50% of variation in damage on living branches. This relationship became much more pronounced (R2 = 0.81) when explored at the mean treatment level; branch manipulation did not alter the patterns of variation in resistance across pine species or MJ treatments. Irrespective of the assessment procedure, MJ consistently decreased weevil damage in all pine species, with larger reduction in weevil damage in stone and maritime pine than in radiata and Scots pine. Radiata pine was the most resistant while Scots pine was the most susceptible to the pine weevil. Overall, results suggest that using excised plant material is an operative alternative for phenotyping weevil resistance whenever care is taken to maintain the functionality of the excised plant material. This will allow taking advantage of multiple available conifer genetic trials to deepen the ecological genetics of resistance to the pine weevil and to screen for resistance without compromising the long‐term utility of those genetic trials.

The Compared Efficiency of the Traditional Method, Radiography without Contrast and Radiography with Contrast in the Determination of Infestation by Weevil (Sitophilus zeamais) in Maize Seeds.

Technologies that increase safety and efficiency, while facilitating and streamlining the work of seed analysts, are increasingly required by the seed industry. X-ray image analysis is a technique that has been used in the analysis of grain and seeds because it is fast, accurate and non-destructive. The traditional method to verify the presence of insect damage in seeds involves manual cutting of the seeds, which endangers the safety of the analyst and is time-consuming and repetitive work that leads to visual fatigue. The objective of this study was to compared the efficiency of radiographic analysis with and without contrast in the determination of infestation by Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), at different stages of development, in maize seeds, compared to the traditional method required by seed legislation, which consists of cutting and visual evaluation. Seeds were evaluated regarding the presence of eggs/oviposition signs, larvae, pupae, adult insects, insect damage in five infestation periods (5, 18, 33 and 35 days after infestation), while evaluating the total number of seeds infested, comparing the three methods. For characterization of the oviposition stage, the use of contrast was best at all times of infestation. For the larval stage, there was no difference between the evaluation methods; however, at 18 days, larger infestations were observed by the traditional method. At 5 days, the identification of pupae was better by the traditional method and radiography without contrast, while for the identification of adult insects the best method was the use of radiography without contrast. The characterization of the level of infestation with maize weevil damage was best verified using contrast radiography. Radiographic analysis is efficient in the detection of damage caused by S. zeamais in maize seeds. This method of radiographic analysis (with or without contrast) is thus an auxiliary tool to assess the damage and presence of S. zeamais in maize seeds.

Field Diagnosis of Citrus Root Weevil Damage

Root weevils infest citrus groves throughout the citrus growing regions of Florida. Among the eight weevil species that have been identified in Florida citrus groves, five have some potential to cause economic problems for nurserymen and commercial growers. The most important weevil species are Diaprepes root weevil (Diaprepes abbreviatus), southern blue-green citrus root weevil (Pachnaeus litus), and the blue-green citrus root weevil (Pachnaeus opalus). The little leaf notcher (Artipus floridanus) and Fuller rose beetle (Asynonychus godmani) are of less concern, but may be locally important (Fig. 1). This paper will deal with Diaprepes and the blue-green root weevils because they are of major economic importance and frequently occur in citrus groves. This document is HS-1014, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date May 2005.&#x0D; HS-1014/HS260: Field Diagnosis of Citrus Root Weevil Damage (ufl.edu)

Risk of damage by the pine weevil Hylobius abietis in southern Europe: Effects of silvicultural and landscape factors

The pine weevil (Hylobius abietis) is one of the most devastating pests of regenerated coniferous forests in northern and central Europe. Although it is also present and potentially harmful in southern Europe, little attention has been paid to this pest in that region. With the aim of quantifying the potential risk of the pine weevil as a forest pest in southern Europe, we performed an intensive assessment of weevil abundance and damage in 21 Pinus pinaster and P. radiata plantations established in recent coniferous clear-cuts in Galicia (NW Spain), i.e. in the south-western part of the natural distribution of H. abietis. The effect of several silvicultural and landscape factors as modulators of weevil risk was analyzed. Abundance of adult pine weevils was highly variable across the sampling plots, with the number of trapped insects significantly correlated with mean air temperature during each trapping period. Damage rate was, however, fairly constant across the whole study period. No significant relationship between pine weevil abundance and damage was observed. Up to 85% of the planted seedlings were attacked and the mortality rates reached 45% in some plots. No weevil preferences were found between the two pine species. Pine weevil damage was positively related to the amount of slash (logging waste) on the ground and negatively related to the time since clear-felling occurred. Once these factors were accounted for, the abundance of mature coniferous forest in the vicinity (500–2000 m) of the clear-cut significantly and positively affected pine weevil damage. We conclude that a high risk of pine weevil damage does exist in NW Spain. Low-intensity forest management together with the scarcity and discontinuity of mature conifer forest in the region seem to be the reason why this forest pest is largely ignored by forest owners and forest-health services. If the forest sector intensifies in this area, care should be taken to protect pine plantations against this devastating pest.

Evaluating the current integrated pest management recommendations in Canada for carrot weevil (Coleoptera: Curculionidae) and carrot rust fly (Diptera: Psilidae)

AbstractThe primary insect pests in Canadian carrot production are carrot rust fly (Psila rosae (Fabricius); Diptera: Psilidae) and carrot weevil (Listronotus oregonensis (LeConte); Coleoptera: Curculionidae). An integrated pest management programme for these pests exists in Québec and Ontario, where most Canadian carrot (Daucus carota subsp. sativus (Hoffmann) Schübler and Martens; Apiaceae) production occurs. As current carrot insect integrated pest management recommendations are decades old, laboratory and field trials were performed to evaluate the carrot insect integrated pest management recommendations. Carrot weevil populations were evaluated in the laboratory for resistance to the primary product used for control, phosmet. Ontario carrot weevils exhibited negligible mortality when exposed to phosmet compared with &gt; 80% mortality in a susceptible strain. Using data from a carrot integrated pest management programme, weather data was correlated with monitoring and damage data of both pests from historical records. Increased carrot weevil captures were weakly related to increased damage. Carrot weevil damage was reduced by following integrated pest management recommendations in one of three trials. No strong relationship between weather and carrot rust fly captures was identified, suggesting the degree day model for carrot rust fly activity needs revision. In field trials, carrot rust fly damage was negligible despite integrated pest management recommendations for insecticide applications. Future research should include improving carrot weevil monitoring and control and increasing the carrot rust fly action threshold to optimise insecticide applications.